Method of uniting sheets of brass, aluminium, and other metals of high conductivity for heat.



I N. PRUSTLBR. METHOD OF UNITING SHEETSOF BRASS, ALUMINIUM, ANDOTHEBMETALS OF HIGH GONDUQTIVITY FOR HEAT.

r APPLICATION FILED NOV. 11, 1912. 1,1 26,655, Patented Jan. 26, 1915.

FIG. 1. 4 FIG, z.

Ii/fi'newes I l I I4 M um w" fiwizior To all whom it ma UNITED snagsPATENT OFFICE.

NOBIBERT rnosrLER, or BERLIN, GERMANY, nssIGNor To GESELLSGHAFT FURELEKTBOTECHNISCHE INDUSTRIE MIT BEscH A xTEB. HAFTUNG, or BERLIN,GERMANY, A CORPORATION or GERMANY. 1

METHOD OF UNITIN G SHEETS 0F BRASS, ALUMINIUM, AND OTHER METALS OF HIGH'CONDUCTIVITY FOR HEAT.

Specification of Letters Patent.

Patented Jan. 26, 1915.

hpplication filed November 11, 1912. Serial No. 780,737.

concern:

, Be it known t at I, NORBERT PnostrLnn, engineer, a subject of the Kingof Bavaria, residing at Berlin, in the Empire of Germany, have inventeda certain new and useful Improved Method of Uniting Sheets of Brass,Aluminium, and other Metals of High Conductivity for'Heat, of which thefollowing is a specification, reference being had therein to theaccompanying drawing.

My invention relates to a method of uniting thin sheets of brass, Germansilver aluminium and other metals or alloys of high conductivity forheat, that is of a higher heat conductivity than iron. Now, brass beinga typical representative of materials of the above mentioned class Iwish it to be well understood that, when in the following specificationand claims I shall speak of brass for more simplicity, all other alloysor metals having the same properties as to conductivity for heat will bemeant as equivalents for brass.

As is well known, it is old to weld together sheets of iron, steel orother iron alloys with the help of the electric resistance weldingmethod and to produce articles of sheet metal in this manner. Suchwelded sheet metal articles in comparison with articles havin riveted orfolded joints, or joints soldered %y means of special soldering meansorfluxes, show the great advantage of being of greater mechanicalresistance and also of having a pretty smooth surface. Moreover, themanufacture of such articles is relatively simple and in consequencethereof comparatively cheap.

According to the known resistance welding method the welding isperformed in such a way that the sheet iron parts to be united arecaused to overlap more or less at their edges, the overlapping parts arethen subjected to pressure, and, while maintaining the pressure, theelectric current necessary for producing the welding temperature ispassed across said overlapped metallic parts. In the art, however, all,attempts to also electrically unite overlapping sheets of metals oralloys such as brass having a.

greater conductivity for heat than iron, especially thin sheets up to 2millimeters in thickness, remained without success. On trying to unitesuch sheets of'metal with .the

help of a normal welding apparatus, the material situated between theelectrodes, when the welding temperature is reached, is generally thrownaway .from the place where the welding is effected, or at least deepde-' I mentioned drawback, no union of the metals is obtained at all.

The great difficulties which have been experienced in attempting tounite-sheets of brass or the like with the help of the known electricresistance welding method are prin cipally due to the following reasons:The above mentioned metals or alloys have a small electrical resistanceowing to their great conductivity for electricity, so that more currentis needed in order to bring them to a high temperature than in the caseof iron or steel, and the electric resistance is still lessened on thepressure between the parts to be welded being augmented. Further, brassand other similar metals or alloys being good conductors for heat, thesame have a pronounced tendency to conduct off the heat generated by theelectric current, said tendency being increased the more the contactbetween the meeting metallic surfaces become perfect owing to greaterelectrode pressure. However, before all, it is to be considered that theabove mentioned materials such as brass pass within a very smallinterval or range of temperature from a solid into a liquid condition,while iron and steel, when the temperature is raised, become but verygradually soft andmore and more plastic before passing into the liquidcondition. This accounts for the facility with which iron and steel areelectrically welded in comparison with the union of sheets .of brass andthe like.

Based upon the above considerations the process forming the object ofthe present invention consists in uniting or fastening together sheetsof brass or other equivalent alloys .or metals, such as German silver,

aluminium having a higher heat conduc-' overlapping sheets of brass orsimilar material, said electrode pressure not exceeding kilograms (about66 lbs.) Under these circumstances the contacting pieces of metal arefused or melted together rather than welded according to the realmeaning of this word. Consequently, the, present new process may be moreproperly termed a process of fusing or melting together metals than awelding process proper.

- Practically I use according to my process for effecting the union apressure as small as compatible with the elasticity of the mater als,such as sheets of brass, tabe welded, so as to just bring the metallicparts i'nto contact .with each other. For uniting brass sheets of 0.5mm. thickness for example a pressure of 10-15 kilograms (about 22-33lbs.) is used according to the present process. WVhen spot weldingelectrodes are used, which, as is well known in the art, are pin-shaped,the contacting or pressing surface of such electrodes for anelectrode-pressure from 15 to 30 kg. ranges between 2 and 5 millimeters"breadth for the different thicknesses of the transition resistance atthe place to be welded is considerably increased, whereby thedevelopment of heat at said place is correspondingly enhanced. At thesame time,

owing ,to the small electrode pressure, the

conducting off of heat from the metallic sheets in contact toward theback of the electrodes is diminished to a great extent and consequentlya sticking of the work pieces to the electrodes is rendered impossible.Further physical phenomenawhich are not exactly understood at presentalso seem in connection with the explained way of performing the processto account for the success obtained.

The new process may be carried out in different manners as shown by wayof examples in the accompanying drawing forming a part of thisspecification.

Figure 1 shows the uniting of two overlapping sheets of brass orequivalent material by means of two electrode-rollers. Fig. 2 representsthe uniting of two overlapping sheetsof brass or equivalent material bymeans of an upper electrode-roller and a lower rod-shaped elect-rode;Fig. 3 .illustrates the uniting of two sheets .of brass or equivalentmaterial abutting with their lateral edges by means oftwo electroderollers. Fig. 4 shows the uniting of two sheets of brass or equivalentmaterial with abutting lateral edges by means of an upper I like, andillustrating the electrodes and showing diagrammatically the portions ofthe sheets which are melted to effect the uniting of the sheets.

The present method in which an electrode pressure not exceeding 30kilograms (about 66 lbs.) is used may be performed with the help of theusual point or spot welding electrodes. In this case, the union of themetallic sheets is only efi'ected insmall areas separated by areas-notin actual contact as in the ordinary point welding.

- Fig. 5 shows overlapping sheets of brass a and b,- c and d areordinary spot welding electrodes. The special electrode pressure isapplied and maintained during the proper time perpendicularly to theouter flat sur-. face or plane of the sheets.

If seams are to be obtained, the brass sheets a, b to be united arebrought in overlapped condition. between two electroderollers e, f (Fig.2) or between an upper electrode-roller e and a lower rod-shapedelectrode 9 (Fig. 3), and the required small electrode pressure isapplied transversely to the outer flat surfaceor plane of the workpiecesa, 6', while causingthe electric current of proper intensity or bulk topass across said overlapping parts.

In Fig. 3 the sheets a, b of brass or equivalent material are broughtbetween the electrode roller 0, (1 so as to meet together or abut withtheir lateral edges or faces, the uniting operationproper being effectedin the same manner, as according to Figs. 1 and 2. As to be seen eachroller electrode contacts partly with the edge of the sheet a, andpartly with the edge of the sheet 6.

' In Fig. 4 the mode of operation and effect is the same as in Fig. 3with the only difference that an upper electrode roller 0 and a lowerrod-shaped electrode 6 are providedfor performing the uniting process.

For a proper understanding of this present method it must be clearlyappreciated that the action of brass and similar metals or alloys underhigh temperatures is quite difierent from the action of steel and iron,in that the latter assume a plastic condition before becoming liquidunder the influence of high temperatures, and in the welding of steeland iron by what is known as the spot welding process, theresistance toa. plastic. condition, at which-.time the pressure from: theelectrodeswelds; or unites the plates. In. the case ofbrass and metals or alloyshowever, there no. intermediate or plastic stageof the. metal before itreaches a liquid condition, and. brass is similar in, thisrespect to.lead, in. that it. is either solid. or li id., and when solid isturnediinto a liqui condition under themfluence. of. high temperaturewithout first (passing through. a plastic condition, asis acharacteristic on steel. and. iron. With a noper understanding. of thisfundamental difference between the actiornof steel and iron on the onehand and. brassandsimilar metals or alloys ontheother, it will become atonce apparent that the. same process which can be successfully. employedfor the welding of sheets of steel and iron electrically,.as by the spotwelding process, can not be employed for the'uniting. of. brass andsimilar metals or alloys-electricallyandthat the difference in. themethod. employed for the uniting oflthi'n sheets ofbrassand' siin1- larmetals or. alloys is not a difference of degree, but is essentially.- adifference of kind or character oftlie method or rocessitself,

om. the. following, taken in connection with Fig. 6 ofthe drawing.

. In the uniting of thin sheets-of. brass and similar metals or allowsit is essential that the adjacent faces of thesheets-be raised'to asufficiently high temperature to become liquid andmelt togethertoproduce a joining or union of the plates, and it. is.equally essentialthat the. bed or more properly, the interior portion. ofjt e plates ustadjacent the contacting surfaces thereof be not ralsed to a suflicientlyhigh temperature to become liquefied, for if such a liquefied conditionexists in theinterior of' the lat-es between the electrodes, anyappreciab epressure of the electrodes on the plateswould instantlydisplacetheliquid metal between the electrodes and result in a hole oraperture through the plates instead of a uniting or jpining of the same.It must be therefore understood that in order to effect the joining oruniting of thin sheets of brass or the like the temperature of thecontacting. surfaces of the plates must be raised'to a tem eratureexceeding that of the temperature 0 the in terior of the. plates betweenthe electrodes.

Such a condition is brought about by this present process, in that t 'eapplication of a relatively light pressure of the electrodes on theplates'causes what might be termed a. slight contact or what istechnically called a poor contact between the plates themselves whenthey overlap and between the electrodes and the plates, when the platesabut. This slight contact offers a greater resistance to the passage offthe current at. the points'of contact andlocalizes thev heat mgsurfacesbeing greater than the heat generated in the interior of the plates'themselves causes alocalized liquefaction of the plates at thesecontacting surfaces without causing a. liquefaction of the metal in theinterior of the plates, and adjacent to the contacting surface thereofbetween the electrodes. The effect of thisis that the plates are meltedrather than welded together, which melting is localized at thecontacting surfaces of the plates and may or may not occur at the pointof contact with the electrodes when the lates overlap according to thecharacter of t e contact between the electrodes and plates themselves.As a conse quence of this a high pressure of the electrodeson brassplates or the like results in noweld or-melting of the metal, aswhenever the contact between the surfaces of the plates is so intimateas not to offer the proper resistance to the assage of the current tothe contacting sur aces, suflicient heat is not generated to cause amelting of the metal. While on the other hand if the current be of suchcharacter to cause a melting of the metal under an intimate contact andhigh pressure ofthe electrodes, said melting occurs not only at thecontacting surfaces of the plates, but in the interior of the platesthemselves between the electrodes. The pressure of the electrodesinstantly displaces the fluid metal and produces a hole in the platesinstead of a union or joining of the same.

From the foregoing it will be seen that the purpose of'this presentmethod is really to maintain the plates of brass or like metal or alloyata sufficiently light contact to produce a melting temperature at thecontacting surfaces only and-at the same time maintain the interior ofthe plates at less than a melting temperature.

As distinguishing this method from the method of welding steel and ironelectrically it will be understood that it is by no means essential inthe welding of steel and iron to treat the same so that the contactingsurfaces thereof are at a .higher temperature than the interior of theplates between the electrodes, as the heat generated in steel and ironplates is due entirely to theresistance.

ance. to the passage. of the current at the actual contacting surfacesof the steel and iron plates.

As will be seen from Fig. 6 the localized melting of the contactingsurfaces 'of the plates is indicated by a waved line at w, as is alsothe localized melting indicated by a waved line at directly under theelectrodes. The interior of the plates being illustrated in sectionlines the same as the surrounding portions of the plates.

I claim ,y

1. The hereinbefore described process of uniting together thin sheets ofmetals of a higher conductivity for heat than iron, such as brass andlike metals or alloys consisting in bringing together said metallicsheets, exerting perpendicularly to the outer flat surfaces of saidsheets an electrode pressure sufficient to produce a slight contactbetween the plates, and in passing through the plates an electricalcurrent to melt the adjacent contacting surfaces of the sheets.

2. The hereinbefore described process of uniting together thin sheets ofmetal of a higher conductivity for heat than iron, such as brass andlike metals oralloys consisting in bringing together said metallicsheets, exerting perpendicularly to the outer fiat surfaces of saidsheets an electrode pressure suflicient to cause a relatively slightcontact between the adjacent contacting surfaces of the sheets toprovide an increased resistance to the passage of an electrical currentat the contacting surfaces of the sheets, and effecting the uniting ofthe sheets by melting the same at theircontacting surfaces by passing anelectric current through the sheets.

3. The hereinbefore described process of uniting together thin sheets ofmetal of a higher conductivity for heat than iron, such as brass andlike metals or alloys consisting in bringing together said metallicsheets, exerting transversely to the outer fiat surfaces of said sheetsan electrode pressure sufficient to produce a slight contact between theplates and in passing through the plates an electrical current to meltthe adjacent contacting surfaces of the sheets.

'4. The hereinbefore described process of uniting together thin sheetsof a metal of a higher conductivity for heat than iron, such as brassand like metals or alloys consisting in bringing together said metallicsheets, exerting transversely to the outer fiat surfaces of said sheetsan electrode pressure sufilcient to cause a relatively slight contactbetween the adjacent contacting surfaces of the sheets to provide anincreased resistance to the passage of an electriealcurre'nt at thecontacting surfaces of the sheets, and effecting the uniting of thesheets by melting the same at their contacting surfaces by passing anelectric current through the sheets.

' 5. The herein described process of uniting together thin sheets ofbrass and like metals or alloys consisting in bringing said sheetstogether between two electrodes and applying to the said sheets at theelectrodes a pressure sufiicient to cause a relatively slight contactbetween the plates to provide an increased resistance to the passage ofan electrical current at the contacting surfaces of the plates, and inpassing an electrical current from one electrode to the other throughthe plates to cause a localized melting of the metal at the contactingsurfaces of the plates which is the point of increase of electricalresistance to melt the sheets together.

6. The herein described process of uniting together thin sheets of brassand like metals or alloys consisting in bringing together said sheetsbetween two electrodes and in contact therewith, and in maintaining saidsheets in a condition of relatively slight'contact to produce a greaterresistance to the passage of an electrical current at the contacting sur-faces of the plates than in the interior thereof, and in passing anelectrical current through the plates from one electrode to the other ofsufiicient strength to cause an increased resistance to the passage ofthe current at the contacting surfaces of the'plates to melt the same.

7. The hereinbefore described process of uniting together thin sheets ofbrass or like metals or alloys consisting in overlapping said sheetsbetween two electrodes and in contact therewith, and in maintaining saidsheets in a condition of relatively slight contact to produce a greaterresistance to the passage of an electrical current at the contactingsurfaces of the plates than in the interior thereof, and in passing anelectrical current through'the plates from one electrode to the other ofsutiicient strength to cause an increased resistanceto the passage ofthe current at the contacting surfaces of the plates to cause alocalized melting of the metal at the contacting surfaces of the plates.

8. The hereinbefore described process of uniting together thin sheets ofbrass and .like metals or alloys consisting in overlapping said sheetsbetween two electrodes arranged perpendicularly to the plane of thesheets and in contact with said electrodes, and in maintaining saidsheets in a condition of relatively slight contact to produce a greaterresistance to the passage of an electrical current at the contactingsurfaces of the plates than in the interior thereof, and in passing anelectrical current through the plates from one electrode to the other ofsufficient strength to cause an increased resistance to the passage ofthe current at the contacting surfaces of the plates to cause alocalized melting of the metal at the contacting surfaces of the plates.

9. The herein described process for uniting together thin sheets ofbrass or like metals or alloys consisting in overlapping said sheetsbetween two electrodes arranged transversely to the plane of the sheetsand in contact with said electrodes, and in maintaining said sheets in acondition of relatively slight contact to produce a greater resistanceto the passage of an electrical current at the contacting surfaces ofthe plates than in the interior thereof, and in passing an electricalcurrent through theplates from one electrode to the other of sufficientstrength to cause'an increased resistance to the passage of the currentat the contacting surfaces of the plates to cause a localized melting ofthe metal at the contacting surfaces of the plates.

10; The herein described rocess of uniting together thin sheets 0 brassor like metals or alloys consisting in bringing together said sheetsbetween two electrodes and in contact therewith, and in applying to thesaid sheets at th point of contact with the said sheets a slightpressure so as Y to produce a relatively slight contact between the saidsheets and the electrodes, and

in passing an electrical current through the said sheets from oneelectrode to the other to produce a localized melting of the sheets attheir point of contact with the said electrodes.

11. The method of uniting thin sheets of brass or like metals or alloyswhich consists in bringing said sheets together, pressing said sheetstogether at united with a relativel light pressure sufiicient to makethe surfzices contact at those places but light enough to causesufiicient electrical resistance between the contacting surfaces toproduce a melting temperature during the passage of an electric currentthrough the same at the said contacting surfaces and passing an electriccurrent through said sheets at the places to be united and therebymelting and so uniting the sheets at said places.

In testimony whereof I afiixed my signature inpresence of two witnesses.

N ORBERT PROSTLER. Witnesses HENRY HASPER, WOLDEMAR Ham.

the places to be

